There are three published runs that use ACE to beat the game, which use different glitches.
The
current record run uses a sprite swap to eat a normally-inedible Chuck to get a bad jump from a glitched power-up.
The original
"Executes Arbitrary Code" run uses a sprite swap to stun an object that isn't supposed to be stunnable and has a bad jump in its 'stun' function. More details
here.
The
oldest version uses a bad pointer to a nonexistant sprite in Yoshi's mouth to overwrite part of the stack, which contains the return address to a function related to a swinging platform.
If you want a minimum effort ACE setup to experiment with, you can play one of those movies until the frame before ACE, then take over.
